A friend has a 35' sloop with an unusual (for me) problem. His engine, a Universal, runs well on start up and motoring at 2600 RPM for only about 20 minutes. It then starts losing RPM over the next 10 minutes and then will not run above 2100 RPM. More throttle won't help. If he stops it and it cools down then this whole process starts again; 2600 at first and then the RPM decline. The temp gauge runs at 175* through all of this, never more. He has had the injectors cleaned and fuel pump inspected and tested. He did a compression test (cold) and it took about 8 turns to get max compression. Any thoughts? He is at wits end on this, and as he is a live aboard, this is a problem of real and immediate concern.

Thank you in advance for your thoughts.

Ron